Measurement Accuracy

Lastly some question the ability to estimate accurately carbon
losses and gains from vegetation and soils due to land-use and management
strategies.

At the project level, mounting evidence indicates that measurement
uncertainty is overstated.80 The Intergovernmental Panel on Climate
Change (IPCC) indicates a high confidence that site-level estimates of net
carbon conserved or sequestered under specific management schemes are more
certain than large-scale estimates of carbon fluxes, such as those at the
national level.81 Thus, project-based efforts, if well monitored,
could yield measurable carbon losses and gains due to project activities, The
IPCC defines high confidence as a high degree of consensus among the
report's authors based on "substantial" evidence.82

The main hurdle facing accurate carbon accounting is the cost of
obtaining the measurements. Any project or effort can be monitored and measured
closely, but increasing accuracy raises costs. While there continues to be
uncertainty regarding forest soil carbon, the majority of pilot offset projects
have not included soil in their net carbon estimates.

Studies have pointed to both data sources and methods for tracking
carbon flows over larger areas, which is required for national inventories. One
U.S. study for example, combined regional forest inventories undertaken by the
U.S. Forest Service with ecosystem studies to estimate carbon storage for major
forest types in the United States." These data and methods could be used
to track changes in carbon storage. However, some Annex I countries may lack the
appropriate monitoring systems to track changes in land use and their subsequent
greenhouse gas emissions and reductions, especially if they are not timber
producers, Also, further research is required to determine greenhouse gas flows
over time in forests under various management schemes. Measurement accuracy
remains a key issue for improving national inventories of emissions and
reductions from forests and land-use
change.